Measurements on transverse cooling times and beam profiles in CELSIUS

The CELSIUS accelerator ring is equipped with a magnesium jet profile monitor which has been used to study transverse electron cooling of ion beams. Cooling times were measured by using a theory which takes intrabeam scattering into account. The results agreed with the cooling times derived from the binary model. Mis-alignment between the electron and the ion beams was found to make a hole in the transverse beam emittance which could be observed as a double peak on the beam profile monitor. It was explained by negative cooling times for ions with small emittances.